EXPERIMENT STATION BULLETINS. 



653 



by its genitalia — the female possessing a saw-like ovipositor. The 

 adults are extremely active and fly at the slightest provocation. They 

 are rarely seen by the casual observer during the early part of the sea- 

 son, but during August of favorable years they are seen to rise up in 

 clouds as one walks down the rows of a potato field. 



Eggs: The eggs of the potato leafhopper are minute pointed ovals 

 approximately 1/32 of an inch long, and are usually laid in the midribs 

 of the potato leaflets. Some of them may be laid in the leaf petioles 

 and in the stems, but ordinarily the leafhopper female selects tlie more 

 tender midribs for oviposition. When first laid, the eggs can be lo- 

 cated only with great difficulty, but near the end of the incubation 

 period their location can sometimes be recognized by slight blister-like 

 elevations on the distorted midribs (Fig. 6). At this period, when 



Fig. 6. Egg of potato leafhopper laid in midrib of potato leaflet. 



viewed through transmitted light with the aid of a hand lens, the eye 

 of the developing embryo shows up as a reddish dot in contrast to the 

 hyaline or green color of the remainder of the developing nymph which 

 cannot be differentiated from the surrounding tissue. Razor sections 

 of an egg-blister at this stage reveal under the microscope a hyaline 

 embryo with a red eye. (Fig. 7). 



Nymphs: The nymphs when hatched are less than 1/25 of an inch 

 long and are white or almost hyaline. The red eyes stand out in strik- 

 ing contrast to the color of the remainder of the insect. Soon after 

 beginning to feed, the nymphs take on a greenish color and during the 

 course of growth the eyes become pearly white. During their growth 

 the nymphs undergo five molts aud the cast skins are often found 

 clinging to the undersides of infested leaves. (Fig. 4). After the third 

 molt rudimentaiy wings begin to develop. During the fourth and 

 fifth instars the nJ^uphs are able to hop from one leaf to another. On 

 casting the last nymphal skin, the wings of the adult leafhopper are 

 found to be curled upward in four separate rolls. The rolls containing 

 the outer wings, or elytra, are transparent, while the rolls containing 

 the hind wings are white. The elytra rolls unfurl about a minute after 

 the insect has emerged from the nymphal skin, while the hind wings 



